State-of-the-art genotyping, with its reliance on high throughput PCR and partial automation, is most efficiently carried our in a core laboratory that contains appropriate specialized equipment and staffed by people experienced with the relevant protocols and problems and that is organized for this work. Concentration of genotyping in Core B will also decrease supply costs for the overall Program Project by encouraging bulk purchases of reagents and supplies for use in quantitative trait locus (QTL)1 mapping projects for complex polygenic traits, for construction of primary genetic maps and for sequencing. As gene mapping focuses on specific candidate regions, the work to identify genes underlying atherosclerosis will increasing depend on DNA sequencing to characterize clones, to identify sequence homologies between human and rodent models, and to locate sequence variants leading to differences in gene function. The role for this core is to support all the projects in their requirements for gene mapping and sequencing. Support will be provided by several means with emphasis placed on: 1) High volume scoring of PCR polymorphisms in humans and mice; and 2) the processing and analysis of dideoxy=terminated sequencing reactions produced by the individual projects. In addition, the core will aid the projects in the preparation of genotype and sequence data in formats most useful for further analysis. Human mapping data will be formatted for forwarding to the Biostatistics Core (Core D). For mouse genotype data, the core will assist the individual projects in linkage analysis by Map Manager.